Harness construction for metal arc type lamp



J n- 2 1969 w. c. GUNGLE ET AL 3,424,935

I HARNESS CONSTRUCTION FOR METAL ARC TYPE LAMP Ora Sheet Filed April 19. 1965 FIG.|

INVENTORS WARREN C. GUNGLE CARL. L. PETERSON .JOH E w YMOUTH ATToR EY Jan. 28, 1969 x w. c. GUNGLE ET AL 3,424,935

HARNESS CONSTRUCTION FOR METAL ARC TYPE LAMP Filed April 19, 1965 sheet 2 of 2 INVENTORS WARREN C. GUNGLE CARL L. PETERSON JOHN F. WAYMOUTH ATTORN Y United States Patent 3,424,935 HARNESS CONSTRUCTION FOR METAL ARC TYPE LAMP Warren C. Gungle, Danvers, Carl L. Peterson, Gloucester, and John F. Waymouth, Marblehead, Mass., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Apr. 19, 1965, Ser. No. 448,964 U.S. Cl. 313-227 11 Claims Int. Cl. H013 61/04 ABSTRACT OF THE DISCLOSURE A high pressure electric discharge device having a filling in the arc tube including a halogen and sodium in which the migration of sodium through the walls of the arc tube is reduced by eliminating the side arms which support the arc tube in an outer envelope and by positioning a current conveying wire to one end of the arc tube adjacent the internal surface of the outer envelope. By this arrangement of parts the loss rate of sodium through the walls of the arc tube is reduced to less than about 0.24 milligram per thousand hours of lamp operation.

This invention relates to high pressure electric discharge devices and particularly to those devices which have a filling in the arc tube which includes mercury, iodine, a light emitting metal and sodium.

In the past few years, research has been conducted to change the emission color of high pressure electric discharge devices. Prior art devices, contained mercury vapor exclusively, and the discharge produced by them was the typical mercury discharge consisting of discrete, separate wavelengths, generally called lines. A1- most all of the radiation of those devices was contained in the blue region, together with a line in the green and two lines in the yellow. Hence, when the high pressure mercury discharge devices of the prior art illuminated a red object, particularly one reflecting light only in the range of 6000 to 6800 A., the object appeared black.

Attempts have been made by the art to obviate this problem and among the suggested modifications has been to include in the mercury arc stream, various metallic elements which emit radiation at wavelengths different than mercury emission. Thus, lamps having such inclusions would produce radiations resulting from a combination of mercury lines together with lines of the metallic additions. For example, thallium, zinc, cadmium, or sodium metals have been added to the arc stream. Although these additions did add other lines to the spectrum and improve the color rendition of the lamp, still only a series of separate and discrete lines were generally present. A light source derived from a large number of lines was yet to be obtained from them.

The art then discovered that phosphors could be placed on the inner surface of the lamp envelope so that some of the ultraviolet radiation of the device could be converted into visible light, particularly in the red, if that phosphor was used. Then the blue emission of the mercury discharge was supplemented with the reddish emission of the phosphor and a reasonable white light was produced by the lamp. But this did not fully solve all of the problems of the device since the core of the problem lay in the failure of the mercury discharge to produce balanced light by itself. Moreover, phosphor coatings tended to produce a loss in efficiency of the lamp because the phosphor absorbed some of the visible radiation from the mercury discharge.

It was then found that the emission color of the are stream could be changed by adding halogens, particuice larly iodine, together with metals whose halides have high vapor pressures and a multiplicity of emission lines in the visible spectrum. Unfortunately, the operating voltages of these devices tended to be rather high and they could not be installed in existing lamp installations as replacements. It was then discovered that if sodium atoms were added to the arc tube, that the operating voltages could be reduced. However, this addition tended to prove troublesome because it was discovered that the sodium ions migrated out of the arc tube during lamp operation. They migrated right through the quartz envelope and into the lamps outer jacket. Thus when the sodium ions migrated from the arc tube, they were not available to continue their work preventing a high operating voltage. Operating lamp voltage is an inverse function of the sodium content of the discharge.

We have now discovered that the construction of the lamp harness, particularly the side rods of the metallic supporting assembly of the arc tube, such as shown in the patent to Gustin No. 3,094,620, tends to increase the rate of sodium migration from the arc tube. These rods are generally situated within approximately 2 centimeters of the arc tube wall and carry current from the outer end of the arc tube back to the base of the lamp. Since these side rods are electrically connected to one electrode of the arc tube, a potential exists between them and the inner surface of the arc tube. Measurement using 1000 watt lamps has shown that a D.C. potential of approximately volts exists, of such a polarity that the inside surface of the quartz is negative with respect to the side rods. Thus any positive ions present in the quartz will have a force exerted upon them forcing them outward through the quartz. When positive ions of alkali metal, particularly sodium, are used in the arc tube, migration through the quartz wall occurs due to this force. When these ions arrive at the outside surface, they are neutralized by photoelectrons emitted from the side rods. If it were not for the neutralization of these positive ions by photoelectrons from the side rods, the accumulation of positive charge on the outside surface of the quartz due to the arriving ions would repel positive ions and prevent the subsequent migration of any more sodium ions through the quartz. Thus the completion of the DC. electric circuit by photoelectrons emitted from the side rods is a major factor in the rapid electrolytic loss of sodium metal from the arc tube. Further, the sodium atoms which result from neutralized sodium ions immediately evaporate due to their high vapor pressure, since the temperature of the outer wall of the arc tube is approximately 800 C. They then deposit on the relatively cool outer bulbous envelope as a coating.

Measurement using radioactive sodium as a tracer have shown that with conventional construction a loss of approximately 1.0 mg. of sodium metal results in one thousand hours. When the side rods are moved to within of the wall of the quartz envelope, the loss rate is approximately 2.0 mg. per thousand hours. Moreover, the distribution of sodium within the quartz itself shows pronounced maxima in the outside surface opposite the locations of the side rods, indicating that electric forces are attracting the positive sodium ions to these areas of the outside surface.

When the side rods of the arc tube harness are eliminated, part of the circuit will be broken; that is, a major source of electrons to recombine with sodium ions is eliminated. Any current now flowing will, of necessity, occur between the leads of either end of the arc tube and the arc tube walls. In addition, when the arc tube harness is constructed in the manner as set forth, arcing between conducting members having opposite polarity is substantially eliminated. A detailed discussion of the problem is stated in the application of Gustin, Ser. No. 188,091,

3 filed Apr. 17, 1962 now Patent No. 3,222,556 and assigned to the same assignee as the instant application.

Accordingly, the primary object of our invention is the elimination of the electrolytic migration of sodium through the quartz walls of an arc tube.

Another object of our invention is the stabilization of operating voltage of high pressure electric discharge devices containing halides and metals.

A feature of our invention is the elimination of side arms which support a high pressure electric discharge are tube in an outer bulbous envelope.

The many other object-s, features and advantages of our invention will become manifest to those conversant with the art upon reading the following specification when taken is conjunction with the accompanying drawings wherein specific embodiments of our invention are shown and described by way of illustrative examples.

Of these drawings:

FIGURE 1 is an elevational view, partly in cross-section, of one embodiment of the high pressure electric discharge device according to our invention.

FIGURE 2 is a cross-section view, partly in cross-section, of another embodiment of the high pressure electric discharge device according to our invention.

Referring now to FIGURE 1 of the drawings, the lamp includes a generally tubular outer bulbous enevolpe 1 having a bulbous central portion and a conventional base 14 attached to the bot-tom thereof. Extending inwardly from the base and inside of the envelope 1 is a mount 15 having .a pair of stiff lead-in wires 12 and 1 6 in electrical conducting relation with the base 14. Disposed upon one of the stiff lead-in wires 12 is a lower, U-shaped support 8 welded there-to. The U-shaped support 8 comprises a pair of vertical wires 23 and 24 rising from a horizontal base 14 wire 25. The upper ends of the lower U-shaped support 8 are welded together with a lower strap 7 which in turn supports an arc tube 2. Preferably, the lower strap includes two sections abutting against either side of the arc tube 2 thereby holding it firmly in place. They touch only the press seal of the are tube and not the body. Generally, both sides of the lower strap 7 can be of identical construction. A pair of bumpers 26 are welded to the lower U-shaped support 8 and abut against the tubular portion of walls of the outer-bulbous envelope 1 thereby stabilizing the structure within the lamp. Preferably, these bumpers are made of a resilient material so that if the lamp is jarred they will absorb much of the shock.

Since the lower U-shaped support 8 is electric-ally connected to the stiff lead-in wire 12, the support 8 forms part of the circuit in the device. Current passes from the base 14 into the lower U-shaped support 8 and thence to lead-in wire 21 which in turn is connected to a cathode 4 in the arc tube. It is sometimes desirable to place an insulating shield about the lead-in wire 21 to prevent arcing within the lamp and between the various elements. Current passes from the lead-in wire 21 to the cathode 4 through an intermediary molybdenum toil section '6.

The other side of the circuit is formed through the stiff lead-in wire 16 which is preferably bent out of place so that parts on one side of the line are insulated from those on the other side. A resistor 13 is attached to the stiff lead-in wire 16 through a lead-in wire associated therewith and thence to a connector 27 which in turn leads through a molybdenum foil section 6 to a starting probe 5. A bimetal 22 is disposed between lead-in 21 attached to the cathode 4 and the 1ead-in wire 27 which is attached to the starting probe 5. The bimetal 22 is biased open when the lamp is turned off but when the lamp starts, it biases closed against the lead-in wires to the probe thereby establishing the same current potential at the probe 5 and the cathode 4. Such closing prevents electrolysis between the probe and cathode.

At the other end of the arc tube 2, an upper support is mounted within the tubular portion of bulbous envelope 1. The support frame 10 includes a horizontal section 18 having vertical supports 17 and 19 depending downwardly therefrom and attached at the free ends to an upper strap 11 which surrounds the press seal of arc tube 2 and rigidly holds it in place. Prefenably, the construction and disposition of upper strap 11 is similar to lower strap 7. A pair of upper bumpers 9 are mounted upon the vertical sections 17 and 19 of the upper support 10 and resiliently abut against the sides of the tubular portion of the bulbous envelope 1. Such disposition pre'- vents breakage of the lamp if the arc tube is shaken or dropped.

A lead-in wire 28 extends to the outside of the arc tube 2 and is attached at its inner end to a molybdenum foil section 6 and thence to a cathode 3. An electrical connection is made between stiff lead-in wire 16 and lead-in wire 28 through a thin conducting lead 20 which may. be of any suitable conducting material. Preferably, the conducting lead 20 is as distantly removed from the arc tube 2 as possible, generally by bending it around the perimeter of the outer bulbous envelope :1.

Referring now to FIGURE 2 of the drawings, a tubular envelope with a central bulbous portion 30 simliar to that shown in FIGURE 2 has a base 32 disposed at the bottom thereof and including a mount 33. Extending through the mount 33 are a pair of stiff lead-in wires 34 and 35 which can be appropriately bent if desired to attain insulation. Extending upwardly from one of the lead-in wires 35 is a lower support 36 which is attached by welding to strap 37 which surrounds the base of the arc tube 31 and holds it firmly in place. Lead-in wire 42 is welded to lower support 36 so as to establish an electrical connection. Cathode 43 is electrically connected to lead-in wire 42 through molybdenum foil section 51. A resistor 38 is attached to stiff lead-in wire 34 and thence through electrical connector 39 to lead-in wire 40 and to probe 49 through molybdenum foil section 51 which extends through the press seal of the arc tube 31. A bimetal 52 is placed across the rod 36 and the lead-in wire 40 and performs the same function as bimetal 22 shown in FIG- URE 1.

At the other end of the arc tube, an upper strap 50 extends around the press seal of the arc tube 31 and is welded in electrical conducting relationship with upper support 45. Generally, the support straps '37 and 50 are strips of metal, stretched tightly across the press seal of the arc tube 31 to hold it rigidly in place. A brace 47 is attached to the top of upper support '45 and a pair of bumpers 46 abut resiliently against the sides of the tubular portion of the outer bulbous envelope 30.

Electrically, cathode 44 within the arc tube 31 is attached through molybdenum foil 51 to lead-in wire 45 and thence in turn to conducting lead 48 and finally to stiff lead-in wire 34 to complete the circuit.

Similarly, as with the conducting lead described in FIGURE 1, the conducting lead 48 extends as distantly as possible from thearc tube 31 and is near the periphery of the b-ubous envelope 30. Of course, extending the wire distantly from the arc tube 31 can be modified, if desired, particularly in cases where the migration of sodium described heretofore is not too acute. For example, it may be stretched downwardly from some suitable location on the upper support 45 to the stiff lead-in wire 34.

When lamps were made in accordance with the principles of this invention, instead of a loss rate of 1.0 mg. sodium metal per one thousand hours, a loss rate of 0.24 mg. per thousand hours resulted. In addition the-re was a pronounced difference in the distribution of sodium in the outside surface of the quartz envelope of the arc tube. Table I below shows the distribution of sodium in the outside surface of the arc tube in two different lamps, one mounted in a harness with side rods away from the arc tube wall, the other without. The quartz arc tubes were sectioned into eight circumferential sections, of which section 1 was at the top of the horizontally-operating arc tubes, section 5 was at the bottom and 3 and 7 were midway at the sides. In lamp 1, with side rods, the side rods were in the horizontal plane opposite sections 3 and 7.

TABLE I.SODIUM CONCENTRATION IN THE OUTSIDE SURFACE OF THE QUARTZ [Parts per million] "Opposite side rods (Lamp No. 1).

In both lamps the sodium which had been lost from the arc tube upon aging was quantitatively accounted for inside the outer bulbous envelope.

Notice that the major difference in the concentrations of sodium in the outside surface of these two are tubes, which differed by a factor of about ten in the sodium loss rates, is in the sections opposite the side rods in lamp number 1. It is plain that neutralization of sodium ions in these sections by photoelectrons emitted from the side rods has resulted in greatly increased flow of sodium through the quartz to the outside surface, and is the cause of the major difference in sodium loss rates.

It is apparent that modifications and changes can be made within the spirit and scope of the instant invention but it is our intention, however, to be limited only by the spirit and scope of the following claims.

As our invention, we claim:

1. A high pressure electric discharge device comprising: a quartz arc tube containing a fill including mercury atoms, halogen atoms and sodium atoms and having a first electrode disposed at the lower end and a second electrode disposed at the upper and thereof; a generally tubular outer jacket having a bulbous central portion; a first and a second stifr lead-in wire disposed at one end of said jacket; means for supporting said arc tube within said jacket and being arranged so that positively charged sodium ions contained within said arc tube are not substantially attracted thereto, said means for supporting including a lower support for the lower end of said are tube and attached to said first stiff lead-in wire and further including an upper support for the upper end of said arc tube, said upper support being axially supported only by the interposed arc tube, said lower support being in electrical conducting relationship with the first electrode; means for conveying current to said second electrode at the upper end of said arc tube, said means for conveying being a wire attached at one end to said second stiff lead-in wire and at the other end to said second electrode, said wire being distantly spaced from said are tube and adjacent the internal surface of said jacket whereby positively charged ions will not be attracted in substantial quantities from Within said are tube.

2. The device according to claim 1 wherein said upper and said lower supports are a pair of rods.

3. The device according to claim 1 wherein said upper and said lower supports are a pair of U-sh-aped wires.

4. The device according to claim 1 wherein there are a pair of resilient bumpers disposed on the upper support and abutting against the inside of the outer jacket.

5. The device according to claim 4 wherein there are a pair of bumpers disposed on the lower support and abutting against the inside of the outer jacket.

6. A high pressure electric discharge device comprising: a quartz arc tube, containing a fill including halogen and sodium atoms; a generally tubular outer jacket having a central bulbous portion; a base adapted to be screwed into a socket disposed at one end of said jacket; a pair of stiff lead-in wires extending from said base internally into said jackets; a lower support mounted on one of said stiff lead-in wires and attached to said are tube and in electrical connection therewith; an upper support tor said are tube in said jacket; said upper support being spaced from said lower support and being axially held in the upper portion of said jacket only by the interposed arc tube; a wire for conveying current from the other of said stiff lead- .in wires to the upper end of the arc tube; said wire ex tending peripherally adjacent the inner surface of said jacket and being distantly spaced from said are tube and adjacent the jacket Wall, whereby the positively charged sodium ions will not be substantially attracted from within said arc tube to said wire.

7. The device according to claim 6 wherein said upper and lower supports are a pair of rods.

8. The device according to claim 6 wherein said upper and lower supports are a pair of U-shaped wires.

9. The device according to claim 6 wherein there are a pair of resilient bumpers disposed on the upper support and abutting against the inside of the outer jacket.

10. The device according to claim 9 wherein there are a pair of bumpers disposed on the lower support and abutting against the inside of the outer jacket.

11. The device according to claim 6 wherein said current conveying wire means is sufficiently spaced from said are tube to reduce the loss rate of said sodium atoms through the wall of said are tube to less than about 0.24 milligram per thousand hours of lamp operation.

References Cited UNITED STATES PATENTS 2,545,884 3/195'1 Isaacs et al 313-25 X 2,888,585 5/1959 Marrt et al. 313-25 3,325,662 6/196-7 Cook 313-17 FOREIGN PATENTS 631,755 11/1963 Belgium.

OTHER REFERENCES Mercury Lamps, General Electric, T P-109, pp. 1, 5, 16, September 1963.

JAMES W. LAWRENCE, Primary Examiner.

R. F. HOSSFELD, Assistant Examiner.

US. Cl. X.R. 

